1. Field of the Invention
The first to fourth inventions disclosed herein relate to methods of format conversion of digital video signals. The fifth to ninth inventions disclosed herein relate to methods of integrating digital video signals into photographic film material. The tenth invention disclosed herein relates to associated signal processing apparatus. The eleventh and twelfth inventions disclosed herein relate to methods of motion compensated temporal interpolation.
2. Description of the Prior Art Relevant to the First Invention
In video signal production systems in which video signals are combined and/or manipulated, it is necessary that any signals to be combined are of, or are converted to, the same format. Accordingly, format conversion of input signals to the format of the production system and/or format conversion of signals from the production system to a required output format becomes necessary for many applications.
In the case of integration of input 24 frame/s progressive scan format material with input 60 field/s 2:1 interlace scan format material to produce output material primarily in 24 frame/s progressive scan format, it would seem appropriate: (a) to convert the input 24 frame/s progressive scan format to 60 field/s 2:1 interlace scan format; (b) for the production system to operate on the two 60 field/s 2:1 interlace scan format signals to produce a combined 60 field/s 2:1 interlace scan format signal; and (c) to convert the combined signal to 24 frame/s progressive scan format. Preferably, the latter conversion `c` should employ motion compensated temporal interpolation, as described in United Kingdom patent application GB 2231228A in view of the change of frame rate. Also, the former conversion `a` from 24 frame/s progressive scan format to 60 field/s 2:1 interlace scan format should employ motion compensated interpolation, if such is possible, again in view of the change of frame rate. However, there is a risk that motion compensated interpolation may introduce artifacts into the output image, and with two stages of motion compensated interpolation, as suggested above, such artifacts may prove to be unacceptable.